A sprayer-type faucet assembly or fixture has a faucet whose head or outlet end normally sits on a faucet arm to give the device the appearance and function of a standard faucet that dispenses water when the associated valve is opened. In addition the head can be pulled from the support arm to work as a sprayer. To this end the head is connected via a flexible hose that extends back down through the arm to the valve, normally forming a loop under the deck to provide some range of movement for the spray head. Such an arrangement is extremely convenient in that it eliminates the need for a separate sprayer attachment and it allows convenient switchover from mobile spray to fixed faucet. It can be used in a standard kitchen sink, in a beauty-shop setting, and or in any type of application where a sprayer might be needed in addition to a faucet.
The primary disadvantage of such a system, as opposed to the standard nonextensible faucet, is that the spray head can be left in the sink, in fact below the surface of the water therein If the valve is still open and there is a momentary pressure reversal, that is the supply pressure momentarily drops below atmospheric, it is therefore possible for such an arrangement to suck in water from the sink, contaminating the clean water in the supply lines This possibility is an illegal situation that plumbing codes specifically forbid
To avoid this, U.S. Pat. No. 4,827,538 proposes that the pressurizable feed passage that extends from the outlet side of the valve to the inlet end of the hose is provided with a vent valve. This vent valve is constituted as a one-way or check valve provided in a passage having one end opening into the pressurizable feed passage and an opposite vent end opening outside the assembly and set up to normally block flow out the vent end. So long as the feed passage remains pressurized, this vent valve stays closed If pressure in the feed passage drops below atmospheric, however, the vent opens and allows the feed passage to suck in air, not the water in the hose and any water in which the outlet end of the hose is submerged in. Thus in the event of a pressure reversal, the supply line will merely suck in air.
In German patent document 3,805,462 of W. Gnauert (U.S. equivalent abandoned applications 07/301,638 and 07/458,171) such a system is described wherein instead of a single-element check valve serving as vent valve, two cascaded valves are used. This system avoids sprayback when the vent is operated or when pressure is first applied to the feed passage.
With these systems it is necessary to provide a separate restriction or check valve in the supply or feed line in order to limit the intake of air during backflow. This supplementary valve, which is necessary to prevent the aspiration of any liquid in the hose, increases the cost and size of the faucet assembly.